1. Field of the Invention
The present invention relates to an image recording device that discharges a photo-setting ink to form images and a method for recording images.
2. Description of the Related Art
The ink jet recording systems include several recording methods those which use various types of ink, such as water-soluble ink, oil-soluble ink, solvent-soluble ink and ultraviolet-ray curable ink, respectively.
In recent years, the ink jet recording system of the active energy ray curing type has come into the spotlight as an image forming method that can form images even on a base material which poorly absorbs ink. As such an ink, there are two types, namely, one is the solvent type in which a reactive monomer is diluted in water, a water-soluble solvent or an organic solvent selected from various organic solvents and the non-solvent type with which no solvent remains after curing thereof. Among those inks, an ink prepared by diluting a reactive monomer with water is recently in the spotlight in view of tendency of favoring free of volatile organic compositions (VOC), easiness in the preparation of ink and safety issues. In particular, the ink of a type that contains non-volatile water-soluble solvent is in the spotlight because, once the dehydration property of this type of ink has been improved, the curing property thereof will be improved accordingly, whereby it is expected that improvement in the high-speed printing and thus high printing productivity can be realized with this type of ink.
However, on the other hand, in addition to high productivity, there has been coming up also with a need to print images on a paper, such as a copying paper, that is not provided with an ink-image forming layer. As a result, further demands for improving the curing performance of the ink have been raised.
As such an ink of the active energy ray curable type, aqueous inks of the ultraviolet-ray curable type are desirably used. In order to improve the curing performance of such aqueous inks, it is proposed, for example, JP Tokukaihei 7-224241), where the cationic polymerization system is employed, to heat an aqueous ink for 5 to 30 min. at a temperature in a range of 80° C. to 170° C. to thereby achieve the curing and dehydration of the ink in a short period of time (see the paragraph of [0022] in JP Tokukaihei 7-224241).
Besides, a printing method that allows to improve the dehydration performance of an ink is disclosed in JP Tokukai 2000-117960. In this reference, a recording medium that has a given wetting characteristic with pure water and satisfies a property with regard to the absorbable ink volume and an ink to be used for the recording medium are taught (see the paragraphs [0008] to [0010] of JP Tokukai 2000-117960). Furthermore, it is described in this reference that the ink comprising the predetermined materials must be used and a step for removing the used solvent must be included, when an aqueous ink comprising an ultraviolet-ray curable substance was used. Besides, in this step for removing the used solvent, it is described that any of evaporation, drying by heating and washing with water can be employed (see the paragraph [0028] of JP Tokukai 2000-117960), and it is specifically described that washing with water is employed in case of the recording medium that has resistance against heating by means of a microwave oscillator, a far infrared lamp or the like and water (see the paragraph [0075] of JP Tokukai 2000-117960).
By the way, in JP Tokukaihei 7-224241 mentioned above, there is no description on the specific heating section and method for curing and dehydrating the ink in a short period of time and on the improvement of the dehydration performance of the ink.
On the other hand, in JP Tokukai 2000-117960 mentioned above, it is described that a predetermined heating method is carried out in order to improve the dehydration performance of an aqueous ultraviolet-ray curable ink. However, according to that method, there has been such a fear that, if too much severe condition was applied for the dehydration and a recording medium with less strength like a copying paper was used when more faster high-speed printing was required, the recording medium may be folded to cause a trouble in the course of moving the recording medium.